Axially compact coupling for a camshaft phaser actuated by electric motor

Abstract

A camshaft phaser includes a housing with a harmonic gear drive unit disposed therein. The harmonic gear drive unit includes a circular spline and a dynamic spline, a flexspline disposed within the circular spline and the dynamic spline, a wave generator disposed within the flexspline, and a rotational actuator connectable to the wave generator. A coupling adapter is disposed coaxially within the housing bore and fixed to the wave generator and supported in the housing by a bearing which is press fit onto a bearing surface of the coupling adapter. The coupling adapter has a coupling adapter bore with opposing drive lugs extending radially inward therefrom which are axially coincident with the bearing surface. A coupling of the rotational actuator is disposed within the coupling adapter bore and has opposing drive slots which receive the opposing drive lugs, thereby transmitting motion from the coupling to the coupling adapter.

We claim: 
     
       1. A camshaft phaser for controllably varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine, said camshaft phaser comprising:
 a housing having a housing bore with a longitudinal axis; 
 a harmonic gear drive unit disposed within said housing, said harmonic gear drive unit comprising a circular spline and an axially adjacent dynamic spline, a flexspline disposed within said circular spline and said dynamic spline, a wave generator disposed within said flexspline, and a rotational actuator connectable to said wave generator such that rotation of said wave generator causes relative rotation between said circular spline and said dynamic spline, wherein one of said circular spline and said dynamic spline is fixed to said housing in order to prevent relative rotation therebetween; 
 a hub rotatably disposed within said housing axially adjacent to said harmonic gear drive unit and attachable to said camshaft and fixed to the other of said circular spline and said dynamic spline in order to prevent relative rotation therebetween; 
 a coupling adapter coaxial with said housing bore and fixed to said wave generator, said coupling adapter being rotatable about a coupling adapter rotational axis and being supported in said housing by a bearing which is press fit onto a bearing surface of said coupling adapter, said coupling adapter having a coupling adapter bore with opposing drive lugs extending radially inward therefrom which are axially coincident with said bearing surface; and 
 a coupling fixed to a shaft of said rotational actuator, said shaft being rotatable about a rotational actuator rotational axis, said coupling being disposed within said coupling adapter bore and having opposing drive slots for receiving said opposing drive lugs, thereby transmitting rotary motion from said coupling to said coupling adapter; 
 wherein said coupling is sized to allow linear movement of said coupling within said coupling adapter bore along a first misalignment axis that is substantially perpendicular to said coupling adapter rotational axis wherein each of said opposing drive lugs includes opposing lug sidewalls that extend axially and are substantially parallel to each other. 
 
     
     
       2. A camshaft phaser as in  claim 1  wherein each of said drive slots includes opposing slot sidewalls that are crowned toward each other for allowing articulation between said coupling and said coupling adapter about said first misalignment axis. 
     
     
       3. A camshaft phaser as in  claim 2  wherein said shaft is disposed within a receiving bore of said coupling and retained therein by a pin which is substantially perpendicular to said rotational actuator rotational axis and which is received within opposing coupling pin bores of said coupling and within a shaft pin bore of said shaft. 
     
     
       4. A camshaft phaser as in  claim 3  wherein said pin is press fit within one of said shaft pin bore and said coupling pin bores and is in a close sliding fit within the other of said shaft pin bore and said coupling pin bores and wherein said shaft is sized to provide radial clearance with said receiving bore for allowing articulation between said coupling and said coupling adapter about a second misalignment axis which is substantially perpendicular to said rotational actuator rotational axis and said first misalignment axis and also thereby allowing linear movement of said coupling within said coupling adapter along said second misalignment axis. 
     
     
       5. A camshaft phaser for controllably varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine, said camshaft phaser comprising:
 a housing having a housing bore with a longitudinal axis; 
 a harmonic gear drive unit including an input member, an output member, a wave generator disposed within said input member and said output member, and a rotational actuator connected to said wave generator such that rotation of said wave generator causes relative rotation between said input member and said output member; 
 a coupling adapter coaxial with said housing bore and fixed to said wave generator, said coupling adapter being rotatable about a coupling adapter rotational axis and being supported in said housing by a bearing which is press fit onto a bearing surface of said coupling adapter, said coupling adapter having a coupling adapter bore with opposing drive lugs extending radially inward therefrom which are axially coincident with said bearing surface; and 
 a coupling fixed to a shaft of said rotational actuator, said shaft being rotatable about a rotational actuator rotational axis, said coupling being disposed within said coupling adapter bore and having opposing drive slots for receiving said opposing drive lugs, thereby transmitting rotary motion from said coupling to said coupling adapter; 
 wherein said coupling is sized to allow linear movement of said coupling within said coupling adapter bore along a first misalignment axis that is substantially perpendicular to said coupling adapter rotational axis wherein each of said opposing drive lugs includes opposing lug sidewalls that extend axially and are substantially parallel to each other. 
 
     
     
       6. A camshaft phaser as in  claim 5  wherein each of said drive slots includes opposing slot sidewalls that are crowned toward each other for allowing articulation between said coupling and said coupling adapter about said first misalignment axis. 
     
     
       7. A camshaft phaser as in  claim 6  wherein said shaft is disposed within a receiving bore of said coupling and retained therein by a pin which is substantially perpendicular to said rotational actuator rotational axis and which is received within opposing coupling pin bores of said coupling and within a shaft pin bore of said shaft. 
     
     
       8. A camshaft phaser as in  claim 7  wherein said pin is press fit within one of said shaft pin bore and said coupling pin bores and is in a close sliding fit within the other of said shaft pin bore and said coupling pin bores and wherein said shaft is sized to provide radial clearance with said receiving bore for allowing articulation between said coupling and said coupling adapter about a second misalignment axis which is substantially perpendicular to said rotational actuator rotational axis and said first misalignment axis and also thereby allowing linear movement of said coupling within said coupling adapter along said second misalignment axis. 
     
     
       9. A camshaft phaser for controllably varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine, said camshaft phaser comprising:
 a housing having a housing bore with a longitudinal axis; 
 a gear drive unit disposed within said housing, said gear drive unit having an input gear member and an output gear member, the input gear member being attachable to said crankshaft and being attached to an output shaft of an electric motor, the output gear being attachable to said camshaft such that rotation of said input gear member by said electric motor causes relative rotation between said crankshaft and said camshaft; 
 a coupling adapter fixed to said input gear member, said coupling adapter being rotatable about a coupling adapter rotational axis and being supported in said housing by a bearing which is press fit onto a bearing surface of said coupling adapter, said coupling adapter having a coupling adapter bore with opposing drive lugs extending radially inward therefrom which are axially coincident with said bearing surface; and 
 a coupling fixed to said output shaft of said electric motor, said output shaft being rotatable about a rotational actuator rotational axis, said coupling being disposed within said coupling adapter bore and having opposing drive slots for receiving said opposing drive lugs, thereby transmitting rotary motion from said coupling to said coupling adapter; 
 wherein said coupling is sized to allow linear movement of said coupling within said coupling adapter bore along a first misalignment axis that is substantially perpendicular to said coupling adapter rotational axis wherein each of said opposing drive lugs includes opposing lug sidewalls that extend axially and are substantially parallel to each other. 
 
     
     
       10. A camshaft phaser as in  claim 9  wherein each of said drive slots includes opposing slot sidewalls that are crowned toward each other for allowing articulation between said coupling and said coupling adapter about said first misalignment axis. 
     
     
       11. A camshaft phaser as in  claim 10  wherein said output shaft is disposed within a receiving bore of said coupling and retained therein by a pin which is substantially perpendicular to said rotational actuator rotational axis and which is received within opposing coupling pin bores of said coupling and within a shaft pin bore of said output shaft. 
     
     
       12. A camshaft phaser as in  claim 11  wherein said pin is press fit within one of said shaft pin bore and said coupling pin bores and is in a close sliding fit within the other of said shaft pin bore and said coupling pin bores and wherein said output shaft is sized to provide radial clearance with said receiving bore for allowing articulation between said coupling and said coupling adapter about a second misalignment axis which is substantially perpendicular to said rotational actuator rotational axis and said first misalignment axis and also thereby allowing linear movement of said coupling within said coupling adapter along said second misalignment axis.